"The justices on Monday declined to reconsider a lower court ruling that the law violates a woman's constitutionally protected right to terminate a pregnancy before a fetus is able to survive outside the womb.

" 'Viability' of a fetus is generally considered to start at 24 weeks. Normal pregnancies run about 40 weeks.

"Gov. Jan Brewer signed the ban into law in April 2012. Nine other states have enacted similar bans starting at 20 weeks or even earlier."

Update at 11:25 a.m. ET. The Broader View:

NPR's Julie Rovner tells Morning Edition that this decision by the Supreme Court tells us "something but not a whole lot" about the potential fate of similar regulations in about a dozen other states.

Arizona, she explained, was a kind of outlier because it was measuring the gestation period differently. Essentially, Julie said, Arizona was banning most abortions at what most medical professionals consider 18 weeks of gestation, weeks before what the Supreme Court and some medical professionals consider a fetus viable.

So, Julie said, we may have to wait for another state's case to reach the high court before making a judgment on what this means nationally.

Concurring with the majority opinion handed down by the United States Court of Appeals for the 9th Circuit, in San Francisco, Judge Andrew J. Kleinfeld said previous Supreme Court decisions forced him to strike down the ban on most abortions after 20 weeks, which is when the Arizona law's sponsors say fetuses can feel pain.

The Times adds:

"[Kleinfeld] questioned the constitutional significance of fetal viability, calling it 'an odd rule, because viability changes as medicine changes.' Since the Roe decision, viability has dropped from about 28 weeks, he said, as doctors become able to save ever younger premature babies.

"Judge Kleinfeld added that the justifications offered for the Arizona law were insufficient.

" 'Were the statute limited to protecting fetuses from unnecessary infliction of excruciating pain before their death,' Judge Kleinfeld wrote, 'Arizona might regulate abortions at or after 20 weeks by requiring anesthetization of the fetuses about to be killed, much as it requires anesthetization of prisoners prior to killing them when the death penalty is carried out.' "